T-Mobile is buying airwaves from Comcast in a deal valued at up to $3.3 billion. In a blog post on Comcast’s site, the company explains that it will sell spectrum in the 600MHz band as it is “unlikely” to need it.

Comcast announced plans to build out a 5G network for its Xfinity Mobile service last year using spectrum in the 600MHz band and CBRS — an unlicensed spectrum in the 3.5GHz range that companies can use for free. However, Comcast says 5G field tests with CBRS spectrum “exceeded” its expectations and that it’s “found the band to be highly efficient and a significant part of a 5G network.”

That’s why Comcast no longer sees a use for its 600MHz spectrum, which it says T-Mobile will lease to purchase. As part of the deal, T-Mobile will pay quarterly lease payments “followed by a final payment of roughly $3.3 billion” to purchase the license.

A filing with the Securities and Exchange Commission confirms that T-Mobile plans to acquire the spectrum, adding that the carrier expects the deal to close in 2028, depending on approval from the Federal Communications Commission. The spectrum will cover major cities like New York, New York; Orlando, Florida; Kansas City, Missouri; and more.

There’s still a chance that Comcast will want to claw some of the 600MHz airwaves back, as it notes it has “secured the option to reclaim” the spectrum if it decides it might need the spectrum in the future. T-Mobile has used 600Mhz spectrum to build out its 5G network in the past. It first switched on its low-band 600MHz 5G network in 2019, which blankets many parts of the US, and spent an additional $3.5 billion on 600MHz spectrum last August.